CN100366657C - Buffering layer material for organic/high molecule luminous diode - Google Patents

Abstract

The present invention relates to a material molecule of a buffering layer for an organic/high molecular light emitting diode (called as OLED/PLED for short) device. The material molecule comprises a plurality of conjugation aromatic rings with semiconductor property (or thiophene rings) and polar groups of philic inorganic materials, and therefore, the material molecule has amphipathic property that the material molecule is philic with an electrode and an organic layer at the same time; the interfacial contact of an organic / high molecular light emitting layer and electrode material which comprises a positive electrode (which are generally an indium and tin oxide (ITO)) and a negative electrode (made of lower work enthalpy metal materials of Mg/Ag (magnesium / silver), etc.) is improved, and a film can be formed by a solution rotating and coating method. The introduced buffering layer can increase the injection capability and the balance transmission of electric charge, and can further improve the efficiency and the stability of the OLED/PLED, and the driving voltage of the device is reduced.

Description

The cushioning layer material that is used for organic/polymer LED

Technical field

The invention belongs to technical field of polymer materials, be specifically related to a kind of cushioning layer material that improves organic/polymer LED (being called for short OLED/PLED) luminous efficiency and stability.

Background technology

Since at first having delivered with organic materials, Kodak in 1987 makes photodiode (Tang CW., J.Appl.Phys.65, (1989) 3610), and then univ cambridge uk has reported under the low voltage (BURROUGHES JH since the phenomenon of high molecule electroluminescent nineteen ninety, NATURE, 347 (1990) 539), the OLED/PLED technical development is very rapid.Compare with liquid-crystal display, this brand-new technique of display has thinner lighter, active illuminating (promptly not needing backlight), wide viewing angle, high-resolution, response low, low temperature and anti-seismic performance excellence, the low manufacturing cost of potential of (molecular device), energy consumption and information such as flexibility and environmental protection design show and device is made desired nearly all advantageous feature fast, is considered to the very strong selection of technique of display of future generation.

But stability (stability) and efficient (efficiency) that to influence the most widely used bottleneck factor of OLED/PLED at present be device, and wherein device efficiency is the factor of core.Around raising the efficiency, people have done a large amount of work, and wherein the use of buffer layer is an important thinking.S.A.Van Slyke (S.A.Van Slyke, Appl.Phys.Lett., 69 (1996) 2160) that initial use is the Phthalocyanine (CuPc that uses at the interface of anode and organic luminous layer, phthalein cyanogen copper), device architecture is MgAg/AlQ (750A)/NPB (600A)/CuPc/ITO, make efficient and stability improve greatly, and the life-span was reached more than 1000 hours.The anode buffer layer that also has a kind of frequent use is two component system: PEDOT:PSS (polyethylene dioxythiophene-polystyrene sulfonate).Scott JC had once investigated this class as cushioning material two component systems (Scott JC, Appl.Phys.Lett., 70 (1997) 2067).People began sight is turned to gradually the buffer layer of negative electrode again afterwards, such as (ITO)/triphenyl diamine (TPD)/8-tris-hydroxyquino-line AluminumAlq (3)/Al ₂O ₃/ Al (Li F, Tang H, Anderegg J, Shinar J, Appl.Phys.Lett., 70 (1997) 1233) and Al/LiF buffer layer, ( L.S.Hung, C.W.Tang, and M.G.Mason, Appl.Phys.Lett., 70 (1997) 152), LiF, Al ₂O3 etc. are insulating material, and are non-conductive, but by tunneling effect, can make voltage descend on the contrary, and current density is improved, and promotes the injection of current carrier.General explanation now is that the introducing of buffer layer makes the injection barrier of current carrier reduce, and it is big that current density becomes.And transport and can reach the raising balance, thereby improve the composite efficiency of current carrier, improve luminous efficiency, reduce operating voltage, and then improve the stability of device.But above-mentioned cushioning layer material function ratio is more single, makes the device architecture more complicated.

Summary of the invention

The objective of the invention is to design and a kind ofly can be compounded in an organic/polymer LED cushioning layer material on the molecule to a plurality of functions,, further improve the luminous efficiency and the stability of device to simplify device architecture.

The OLED/PLED cushioning layer material of the present invention's design, be the novel poly-fluorenes of a kind of structure, polyphenyl, Polythiophene, poly-fluorenes support, polyphenylene derivatives, be made of non-conductive polar group Y on poly-fluorenes, polyphenyl, Polythiophene, poly-fluorenes support, polyhenylene equiconjugate unit one side joint, its general structure is as follows:

Wherein Ar is unit a kind of of following conjugacy: (1) gathers fluorenes, (2) polyphenyl, and (3) Polythiophene, (4) poly-fluorenes support, (5) polyhenylene, its structural formula is as follows respectively:

In the above-mentioned materials, non-conductive polar group Y can be CH ₂OH or CH ₂NH ₂, its structural formula is exemplified below:

In the above-mentioned materials, the polymerization degree n of conjugate unit Ar generally 8 to more than 10, to guarantee semi-conductive characteristic.

In the above-mentioned materials, the R among the conjugate unit Ar can be C ₆H ₁₃, C ₈H ₁₇Or C ₁₂H ₂₅A kind of.

Its effect of the cushioning layer material molecule of the present invention's design and characteristics are as follows:

(1) introducing non-conductive polar group Y in molecule, mainly is to improve to contact with interelectrode interface, similar in the PEDOT:PSS system PSS, the injection that can improve current carrier.Conjugate unit partly be semiconductor property and PEDOT function class seemingly, can improve the transport property of current carrier.

(2) in molecule, contain the conjugate unit part.Poly-fluorenes equiconjugate system is outstanding luminous luminescent material, is semiconductor property, and is favourable to carrier transport.Therefore synthetic buffer layer of the present invention can be simplified device architecture.

(3) molecule contains a plurality of conjugate units, makes its solution have higher viscosity on the one hand, can use the method film forming of solution spin coating, improves the workability of material.On the other hand, a plurality of conjugate units can improve the conduction property of material.

Embodiment

The invention is further illustrated by the following examples material and synthetic.

Embodiment 1

The poly-fluorenes cushioning layer material of hydroxyl end, its structural formula is:

The above-mentioned materials synthetic route is as follows shown in the formula:

The step of concrete reaction is:

The first step, system temperature is reduced to-78 ℃, in the THF solution of (1), the n-Butyl Lithium of amount such as dropping lentamente, add excessive triisopropyl boric acid ester again after, rise to room temperature, and reaction is spent the night, use hydrochloric acid hydrolysis then, at last through the extracting and washing drying separate material (2), productive rate is 75%.

In second step, in the DMF solution of (2), add excessive N a ₂CO ₃With the catalyzer four triphenyl phosphorus palladiums of trace, be heated to 120 ℃ and refluxed 24 hours, add a spot of end-capping reagent bromobenzene again, refluxed again 6 hours, at last through the washing drying separate material (3), productive rate is 80%.

The 3rd step, toward etc. in the toluene solution of (3) of amount and 4-boric acid phenylcarbinol, adding excessive N a ₂CO ₃With the catalyzer four triphenyl phosphorus palladiums of trace, be heated to 120 ℃ and refluxed 24 hours, again through the washing drying separate material (4), productive rate is 96%.

The 4th step, with etc. (4), polyoxyethylene glycol (PEG) and phenylene diisocyanate (TDI) naphthalene or the vulcabond (MDI) of amount be dissolved among the THF, be heated to 70 ℃ to reflux 8 hours, at last through the dry polymkeric substance (5) that gets of washing.Claim buffer1 (being designated as B1) in the present invention

Polymkeric substance (5) is joined following device to be compared:

ITO/B1/Polyflourene/Mg: Ag (-------(device 1) of magnesium: silver)

ITO/Polyflourene/Mg: Ag-------(device 2)

Test shows has added the device of B1, and luminous efficiency improves 30%, and its beginning operating voltage reduces by 0.2 volt.

Embodiment 2

The poly-fluorenes cushioning layer material of amino-contained end, its structural formula is:

It is to prepare as reaction raw materials with the polymkeric substance (5) for preparing among the embodiment 1.Its synthetic route is as follows:

Concrete reactions steps is:

With etc. polymkeric substance (5), quadrol and the HDI (or TDI or MDI) of amount be dissolved in the tetrahydrofuran (THF) (THF), be heated to 70 ℃ to reflux 8 hours, at last through washing dry polymkeric substance (6), be designated as B2 in the present invention.

B2 is added in the following device,

ITO/B2/Polyflourene/Mg∶Ag

Test shows has added the device of B2, and efficient improves 42%, and its beginning operating voltage reduces by 0.3 volt.

Embodiment 3

The polyphenyl cushioning layer material of hydroxyl end, its structural formula is:

The synthetic route of above-mentioned materials is as follows shown in the formula:

The step of concrete reaction is:

The first step, system temperature is reduced to-78 ℃, in the THF solution of material (7), the n-Butyl Lithium of amount such as dropping lentamente, add excessive triisopropyl boric acid ester again after, rise to room temperature, and reaction is spent the night, use hydrochloric acid hydrolysis then, at last through the extracting and washing drying separate material (8), productive rate is 67%.

In second step, in the DMF solution of (8), add excessive N a ₂CO ₃With the catalyzer four triphenyl phosphorus palladiums of trace, be heated to 120 ℃ and refluxed 30 hours, add a spot of end-capping reagent bromobenzene again, refluxed again 8 hours, at last through the washing drying separate material (9), productive rate is 76%.

The 3rd step, toward etc. in the toluene solution of (9) of amount and 4-boric acid phenylcarbinol, adding excessive N a ₂CO ₃With the catalyzer four triphenyl phosphorus palladiums of trace, be heated to 120 ℃ and refluxed 30 hours, again through the washing drying separate material (10), productive rate is 93%.

The 4th step, with etc. (10), polyoxyethylene glycol (PEG) and the HDI (or TDI or MDI) of amount be dissolved among the THF, be heated to 70 ℃ to reflux 8 hours, at last through the dry polymkeric substance (11) that gets of washing.

This material joins in the device as embodiment 1, has the character with the materials similar of embodiment 1.

Embodiment 4

The polyphenyl cushioning layer material of amino-contained end, its structural formula is:

This is to prepare as reaction raw materials with the product (11) for preparing among the embodiment 3, and its synthetic route is as follows:

The step of concrete reaction is:

With etc. polymkeric substance (11), quadrol and the HDI (or TDI or MDI) of amount be dissolved among the THF, be heated to 70 ℃ to reflux 8 hours, at last through washing dry polymkeric substance (12).Be designated as B3 in the present invention.

The performance of more following device:

ITO/B3/PPP/Mg: Ag--------(device 5)

ITO/PPP/Mg: Ag-------(device 6)

Test shows, device 5 has than the trigger voltage at the end and higher luminous efficiency than device 6, and the brightness of device 5 is high by 35% under identical operating voltage.

Claims (4)

1. a compound is characterized in that being made of non-conductive polar group Y on poly-fluorenes, polyphenyl, Polythiophene, poly-fluorenes support, polyhenylene one side joint, and its general structure is as follows:

Wherein Ar is unit a kind of of following conjugacy: (1) gathers fluorenes, (2) polyphenyl, and (3) Polythiophene, (4) poly-fluorenes support, (5) polyhenylene,

Its structural formula is as follows respectively:

Said non-conductive polar group Y is CH ₂OH or CH ₂NH ₂

2. compound according to claim 1, the polymerization degree n that it is characterized in that conjugate unit is more than 8.

3. compound according to claim 1 is characterized in that the R in the said conjugate unit is C ₆H ₁₃, C ₈H ₁₇Or C ₁₂H ₂₅A kind of.

4. as the application of compound as described in one of claim 1 to 3 as the OLED/PLED cushioning layer material.